Wireless communication technology has evolved to deliver rich multimedia and video services in addition to the traditional voice and data services. Typical wireless multimedia communications involve the transmission of a continuous source over a noisy channel. Common examples are speech communications, mobile TV, mobile video and broadcast streaming. In such communications, the multimedia source is encoded and compressed into a finite stream of bits, and the bit stream is then communicated over the noisy channel. Source coding is carried out to convert the continuous source into a finite stream of bits, and channel coding is performed to mitigate the errors in the bit stream introduced by the noisy channel. Often, it may be necessary to transmit the source over time-varying wireless channels while satisfying certain end-to-end user quality of experience (QoE) constraints, including average distortion and multimedia quality requirements such as in real-time mobile video streaming. Hence, towards the design of enhanced wireless multimedia communication technologies, it may be preferable to optimize the overall user QoE, instead of optimizing more traditional quality of service (QoS) metrics. In general, QoE degradation may be caused by high distortion levels, limited bandwidth, excessive delay, power constraints, and computational complexity limitation. In such a scenario, separating the compression and channel coding may not be optimal any longer from a user QoE perspective.
To ensure optimality in terms of end-to-end QoE, joint source-channel coding (JSCC) techniques may be used to perform source compression and channel coding in a coordinated fashion. In this context, JSCC techniques may jointly optimize codec and radio parameters to minimize end-to-end distortion. JSCC techniques may support cross-layer capabilities, which may provide support for PHY/MAC/NET-aware bit rate adaptation at the codec level to enable source-channel rate matching, e.g., as in adaptive streaming technology widely adopted today in many commercial multimedia delivery systems. Such a cross-layer capability can benefit from signaling techniques that feedback QoE parameters from the client to the server such as real-time control protocol (RTCP), standardized by the Internet Engineering Task Force (IETF) in RFC 3551 specification and also used in both packet-switched streaming (PSS) and multimedia broadcast and multicast services (MBMS) Third Generation Partnership Project (3GPP) specifications (TS 26.234 and TS 26.346, respectively). Such QoE feedback signaling mechanisms may allow streaming service to adapt the bit rate based on varying network conditions (e.g., changing resource availability, time-varying nature of the wireless channel) to ensure higher QoE while maintaining interrupt-free playback. However, the current wireless communication systems such as those specified in Worldwide Interoperability for Microwave Access (WiMAX) and/or Long Term Evolution (LTE) standards do not support cross-layer functionalities required to provide application oriented QoE values for multimedia delivery and enable application-aware PHY/MAC/NET layer adaptation, including application-aware radio resource management and application-aware routing and network control. In particular, in current WiMAX and LTE standards, the network does not pass any content-specific information (e.g., rate-distortion characteristics of the video stream, associated video quality metrics, etc.) regarding the multimedia processing at the codec to the radio access network and core network. Instead, the PHY/MAC/NET layers remain agnostic of application-layer requirements and characteristics and only aim to optimize link quality subject to certain target QoS requirements (e.g., throughput, latency/jitter, packet error/loss rate, etc.).